The present invention relates to a method for detecting a speed in a generator unit as well as to an arithmetic unit, in particular a generator controller, and a computer program for carrying out the method.
Motor vehicles are equipped with an electrical system which is supplied with voltage via an electric machine, e.g. an externally excited synchronous machine, operated as a generator. In order to control the electrical system voltage, an excitation current of the electric machine can be controlled. The electric machine is generally connected to the electrical system via a rectifier and with said rectifier forms a generator unit. Errors such as, e.g., short circuits can occur in such generator units, which errors should be detected whenever possible.
The German patent application DE 10 2015 211 933, which is not pre-published, discloses a method for detecting an error in a generator unit, which comprises an electric machine with a rotor winding and a stator winding and a rectifier connected thereto, via which the electric machine is connected to an electrical system, wherein a voltage of the electrical system is controlled to a target value via an excitation current flowing through the rotor winding of the electric machine and a plot of the excitation current is monitored, and wherein it is concluded that there is an error in the generator unit if an oscillatory plot of the excitation current is detected, wherein a magnitude of the oscillation lies above a threshold value.